I have locks on my bed to secure anything that is stored under it. Also a lock can be placed on the bedroom door making a larger secure room. Unless there is maintenance having to do with those areas there is no reason for a service person to be in there. The basement areas are locked and no need to give the key to service unless they need access for repairs.
Signs have no force of law but oral and written contracts do.
The FB poster needs to post to "Ask Marcus" here on the forum. He is very sensitive about ethics and responsibilities in businesses.